1. Field of the Invention
The present invention relates to a discharging structure, and more especially, to a structure for discharging the extreme ultraviolet mask (EUV mask) during the EUV mask is inspected by the charged particle beam inspection system.
2. Background of the Related Art
Optical inspection of a mask is based on a comparison of the light signals in the patterned regions relative to the non-patterned regions. A high contrast is necessary in order to achieve sufficient sensitivity for defect detection. The transmissive masks used in DUV (deep Ultra Violet) lithography can be inspected without difficulty since the contrast between the opaque regions and the clear regions is high at UV/DUV wavelengths. However, it is difficult to inspect the reflective masks, the EUV mask for example, used in EUV lithography since not only the contrast between the absorber region and the mirror region is low at UV/DUV wavelengths, but also wavelength of the UV/DUV is too lengthy to inspect EUV mask.
Now, a charged particle beam inspection system, an electron beam (E-beam) inspection tool, accordingly, is developed to inspect the EUV mask. However, accumulated charging on EUV mask will induce inspection issue while the EUV mask is inspected by E-beam inspection tool. This issue will not happen to silicon wafer because silicon wafer can be grounded. Substrate of the EUV mask is dielectric, and can not be grounded.